1. Field of the Invention
The present invention relates to a multiple plate clutch device. More specifically, the present invention relates to a multiple plate clutch device having a return spring for returning a piston.
2. Background Information
Generally speaking, conventional multiple plate clutch devices are equipped with a plurality of first and second plates arranged alternately in an axial direction and a piston that is driven by hydraulic pressure. Conventional multiple plate clutch devices press the first and second plates together. Multiple plate clutch devices are used in automatic transmissions and also function as a brake. The multiple plate clutch device is also provided with a return spring for returning the piston and releasing the clutch.
A plurality of coil springs, for example, is used as return springs. The coil springs are disposed in a circle with one end supported by a retaining plate and another end abutting the piston. The retaining plate receives a load from the piston by means of a snap ring fixed axially to a wall surface thereof. As a result, when hydraulic pressure does not act on the piston, the load applied by the return spring returns the piston and releases the engagement of the clutch.
Since the return spring arrangement just described is provided with a retaining plate and a snap ring, the number of parts increases and causes the multiple plate clutch device to be relatively expensive. Furthermore, the axial dimension of the device becomes large because a certain amount of space must be secured in the axial direction in order to arrange the return spring, etc.
In view of the above, there exists a need for a multiple plate clutch device that overcomes the above-mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
An object of the present invention is to conserve space in a multiple plate clutch device.
A multiple plate clutch device in accordance with a first aspect of the present invention has a first member, a second member, a plurality of first plates, a plurality of second plates, a piston, and a return spring. The first member has a plurality of teeth aligned around a circumference thereof. The second member is disposed so as to face the first member in a radial direction. The plurality of first plates has engaging teeth that engage the plurality of teeth of the first member. The plurality of first plates is unable to rotate but able to move in an axial direction relative to the first member. The plurality of second plates is disposed alternately with respect to the plurality of first plates in the axial direction. The second plates non-rotatably engage the second member, and are able to move in the axial direction relative to the second member. The piston presses the first plates and the second plates together. The return spring is disposed inside a groove between the teeth of the first member and pushes the first plate that is closest to the piston toward the piston.
With this multiple plate clutch device, the clutch engages when the piston presses the first and second plates together. When the load on the piston is released, the return spring applies a force on the piston by way of the first plate that is closest to the piston and causes the piston to separate from the first and second plates. As a result, the multiple plate clutch device disengages. Since the return spring is disposed inside a groove between the teeth of the first member, the space conventionally occupied by the return spring can be omitted.
A multiple plate clutch device in accordance with a second aspect of the present invention is the device of the first aspect, wherein the return spring is a flat spring.
This multiple plate clutch device is able to conserve space by using a flat spring. The flat spring mentioned here is a spring made from a thin sheet material that provides a spring effect. More specifically, the flat spring is made of a thin sheet having a thickness of up to approximately 1 mm. The thin sheet is press worked into the desired shape and given a spring effect.
A multiple plate clutch device in accordance with a third aspect of the present invention is the device of the second aspect, wherein the return spring is disposed between an engaging tooth of the first plate that is closest to the piston and an engaging tooth of the first plate that is farthest from the piston.
This multiple plate clutch device does not require a special member to support the return spring because the first plates support the return spring.
A multiple plate clutch device in accordance with a fourth aspect of the present invention is the device of any of the aforementioned aspects, wherein one end of the return spring is held in an engaging tooth of the first plate that is closest to the piston.
In this multiple plate clutch device, the first plate that is closest to the piston determines the position of the return spring.
A multiple plate clutch device in accordance with a fifth aspect of the present invention is the device of the fourth aspect, wherein one end of the return spring is held in the engaging tooth of the first plate that is closest to the piston in such a manner that it cannot fall out.
With this multiple plate clutch device, the return spring and the first plate closest to the piston constitute a subassembly, making handling more convenient.
A multiple plate clutch device in accordance with a sixth aspect of the present invention is the device of the fifth aspect, wherein a slit is provided in the engaging tooth of the first plate that is closest to the piston. Further, the return spring has a claw that is held in the slit provided in the engaging tooth of the first plate that is closest to the piston.
A multiple plate clutch device in accordance with a seventh aspect of the present invention is the device of any of third through sixth aspects, wherein the return spring has a flat section that abuts against an axially facing surface of the engaging tooth of the first plate that is closest to the piston.
In this multiple plate clutch device, the orientation of the first plate that is closest to the piston is stable.
A multiple plate clutch device in accordance with an eighth aspect of the present invention is the device of any of third to seventh aspects, wherein the return spring has a curved part that contacts the engaging tooth of the first plate that is farthest from the piston.
In this multiple plate clutch device, the return spring can deflect smoothly in the axial direction when the clutch is engaged.
A multiple plate clutch device in accordance with a ninth aspect of the present invention is the device of eighth aspect, wherein the return spring has a projection whose movement in the radial direction is restricted by the engaging tooth of the first plate that is farthest from the piston.
These and other objects, features, aspects, and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.